Catalytic reactors that employ catalytic oxidation methods can generate highly exothermic reactions; i.e. reactions that produce a significant quantity of energy in the form of heat. In reactors where a catalyst is positioned on a substrate, this heat may be sufficient to damage the substrate and/or the catalyst.
One strategy developed to protect the substrate and the catalyst is referred to as backside cooling. A backside-cooled substrate generally has two surfaces and permits heat to be conducted therebetween. In most catalytic reactors employing backside cooling, the catalyst is positioned on only one surface of the reactor. During operation, a first fluid to be reacted is passed over the surface with the catalyst and a second fluid, which could be the same as the first fluid, is passed over the other surface.
As heat is generated at the surface on which the catalyst is positioned, the heat is conducted through the substrate from one surface to the other where it is subsequently transferred to the second fluid. The substrate and catalyst therefore are maintained at a temperature below the temperature generated by the heat of reaction.
Some catalytic oxidation methods utilize first and second fluids that are different with the desire to mix these fluids after the first fluid has been oxidized in the presence of the catalyst, thereby forming a first reacted mixture. In particular, certain catalytic reactors have a first fluid that is suitable for the catalytic reaction and a second fluid that is not; e.g. the first fluid is a fuel/oxidant mixture containing the fuel that is to be oxidized to create a reacted mixture, and the second fluid comprises the oxidant.
One known catalytic oxidation method uses a first fluid that is fuel rich and a second fluid that is an oxidant for the fuel in the first mixture. A rich mixture is a mixture having a ratio, generally referred to as a fuel/air equivalence ratio, greater than one, wherein one represents a stoichiometric mixture. When the first mixture is rich, the reacted mixture produced when the first mixture is passed over the catalyst similarly will be rich. It should be noted that the catalytic reaction is limited by the amount of oxidizer present in the first mixture. Accordingly, the catalytic reaction will stop when the oxidizer is depleted to a given level that no longer supports catalytic oxidation. When a second fluid containing oxidant suitable to support oxidation of the fuel in the first fluid is combined with the reacted mixture, the oxidizer level is once again sufficient for the resumption of combustion. The preferred embodiment of such a fuel-rich catalytic reactor is described in detail in U.S. Pat. No. 6,394,791 to Smith, et al. (“the '791 patent”), which patent is incorporated herein by reference, particularly: Column 3, lines 35-42; Column 4, lines 20-62; Column 8, lines 33-37 and 47-54; and Column 12, line 31 to Column 13, line 21. A problem with such reactors is that the catalytic tube can be held in place only at one point. Thus, the tube may move and vibration can become an issue. Further, in these types of catalytic reactors, it is important that the reactor structure facilitate the rapid mixing of the reacted mixture with the second fluid to occur prior to autoignition.
Based on the foregoing, it is the general object of the present invention to provide a catalytic reactor that overcomes the above-identified problems and drawbacks of prior art reactors.